API design
REST APIs on Node.js: contracts, resources, versioning and response codes
- Resources, methods and response codes
- Input validation and error handling
- Versioning and backward compatibility
- Swagger/OpenAPI documentation
// service · backend and REST API
Backend and REST API development
Services and APIs that hold the product together: design, development, integrations and operations
I design and build backends on Node.js: REST APIs in NestJS, Express and Fastify, Python services, data in PostgreSQL, MySQL and Redis. Contracts and Swagger/OpenAPI docs, integrations with CRM, payments and external systems, deployment in Docker
What is included
01
02
Services with NestJS
Modular architecture: controllers, services, DI (dependency injection) and microservices
- NestJS, Express and Fastify
- Modules, dependencies and separated layers
- Python services
- Background jobs and queues
03
Data and cache
PostgreSQL, MySQL and Redis: schemas, migrations, indexes and transactions
- PostgreSQL, MySQL and Redis
- ORM and migrations: Prisma, TypeORM, Knex
- Indexes and query optimisation
- Transactions and data integrity
04
Access and integrations
JWT, role model, webhooks, CRM (U-ON) and payment APIs
- JWT: access and refresh tokens
- Roles and permissions enforced in the API
- Webhooks and CRM (U-ON) synchronisation
- Payment and third-party APIs
Outcome
- A working API in production, not a paper sketch
- Contracts and Swagger/OpenAPI documentation
- Integrations with CRM, payments and third-party services
- A data layer with migrations, indexes and transactions
- Code and tests you can keep building the service on
How the work runs
STEP 01
Brief
Scenarios, load, integrations, constraints and an estimate
STEP 02
Build
Iterations: API contracts, data, integrations, with interim demos
STEP 03
Launch
Deploy, scenario and load checks, go live in production
STEP 04
Operate
Monitoring, backups, support and further development
Related projects
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Common questions
How much does backend and REST API development cost?
It depends on the number of endpoints, integrations and the load. After a short brief I send an estimate broken down by stage, with no hidden work
Can you connect an existing frontend?
Yes. I work from API contracts: describe endpoints in Swagger/OpenAPI, keep backward compatibility and connect the current UI in iterations
Do you build CRM and payment integrations?
Yes: webhooks, lead delivery into CRM (U-ON), payment and third-party APIs, and data exchange with external systems
What about the database and migrations?
PostgreSQL, MySQL and Redis, ORMs Prisma, TypeORM and Knex, migrations, indexes and transactions, backups and recovery